A Study On Interactions Of Iron Nanoparticles And Natural Organic Matter

In-situ injection of nano zero valent iron(nZVI)is a new technology developed forgroundwater remediationin recent years.Natural organic matter(NOM)is a common organic macromolecule mixture in water.During the processes of contaminants treatment using nZVI,the interactions of nZVI-NOM would affect the physical properties of nZVI,such as dispersibility,stability and aggregation,which hereinimpact the migration,degradation performance,reactivity and the fate of nZVI.However,few reports were related to the quantitative study onphysicochemical property of nZVI caused by NOM,especially the aggregation effect.In addition,NOM is a kind of heterogeneous mixture with different molecular weight components,which would selectivelyadsorbed on nZVI and thus affect the behavior of nZVI.Therefore,the effects of NOM on the property of nZVI and the mechanism of NOM-nZVI interactions were studied in this thesis.The main results are concluded as follows:1.The dispersion and stability of nZVI particles with carboxymethyl cellulose coating or bentonite supporting were greatly increased in comparison with barenZVIby the liquid phase reduction method.It effectively hindered the particle aggregation and sedimentation.NOM could adsorb on the surface of nZVI to enhance the electrostatic repulsion,resulting intothe dispersion and inhibition of aggregation.For several kinds of nZVI,HA has the most significant impact on the bentonite supported-nZVI.As the agglomeration decreased,the particle size of nZVI could be reduced to below 100 nm.Similarly,the sedimentation rate slowed down greatly,and the dispersion stability was much improved.2.The adsorption process of Suwannee River Humic Acid(SRHA)and Fulvic Acid(SRFA)on nZVI and nano magnetite(nano-Fe3O4)followed the pseudo-secondary adsorption kinetics.Langmuir isothermal model well described the adsorption process.The adsorption capacity of nZVI for NOM was much higher than that of nano-Fe3O4,showing the maximum adsorption capacity of the former was about three times as much as the latter.Such big different performance might be attributed to the different surface properties,which also indicates that the surface of nZVI was not a dense magnetite layer.3.The results showed that nZVI preferentially adsorbed the medium molecular weight of SRHA but the large molecular weight of SRFA.The different selective adsorption capacity is likely to be related to the aromaticity and hydrophobicity properties with different molecular weight components.These understandings were very important in the practical application of nZVI for contaminated water remediation.